JP5773734B2 - Board pre-inspection method - Google Patents

Description

  The present invention relates to a substrate preliminary inspection method that is performed before performing a process including a step of applying a predetermined stress to a substrate such as a silicon wafer or a glass substrate.

  Various treatments are performed on the substrate in each treatment chamber. Some of these processes include a process in which a strong stress is applied to the substrate, such as a rapid heating of the substrate, and the substrate may break down without being able to withstand the strong stress.

  Here, when stress is applied to the substrate, it is elastic to the substrate by an acoustic emission (AE) phenomenon (a phenomenon in which, when a solid is deformed or destroyed, the strain energy stored up to that point is released and an elastic wave is generated). A wave is generated. Therefore, conventionally, an AE sensor for detecting an elastic wave generated on a substrate is provided, and the processing is immediately stopped when the AE sensor detects an elastic wave generated by the destruction of the substrate (for example, Patent Documents). 1).

  However, when the substrate is broken, laborious maintenance work such as opening the processing chamber and removing the fragments of the substrate is required, and the productivity is greatly reduced.

JP 2004-28823 A

  In view of the above points, an object of the present invention is to provide a substrate pre-inspection method in which a substrate that may cause destruction during processing can be found in advance.

  In order to solve the above-described problems, the present invention is caused by a stress applying step of applying stress to the substrate before performing a process including a step of applying a predetermined stress to the substrate, and stress applied in the stress applying step. A detection step of detecting an elastic wave generated in the substrate due to an acoustic emission phenomenon, and determining whether the substrate can withstand the predetermined stress based on the elastic wave detected in the detection step. To do.

  According to the present invention, it is possible to determine in advance before processing whether a substrate can withstand a predetermined stress applied during processing. Then, by removing a substrate that cannot withstand a predetermined stress as a defective product, the possibility of the substrate being destroyed during processing can be reduced as much as possible.

  Here, when the substrate breaks due to the stress applied thereto, first, a micro crack is generated in the substrate, and the crack grows to break. Therefore, when the elastic wave detected in the detection step includes an elastic wave generated by a micro crack generated before the substrate is broken, it is desirable to determine that the substrate cannot withstand the predetermined stress.

  By the way, the process is a process performed in a processing chamber having a stage having an adsorption unit for adsorbing a substrate and a heating unit for heating the substrate, and the step of applying the predetermined stress adsorbs the substrate to the stage. In the heating step of heating the substrate to a predetermined processing temperature, it is desirable to execute the stress application step and the detection step before the heating step is completed with the substrate placed on the stage.

  Here, it is possible to execute the stress application process and the inspection process in a place different from the processing chamber, but the stress application process and the detection process are performed with the substrate placed on the stage in the processing chamber as described above. In this case, it is not necessary to secure a separate place for preliminary inspection, and space saving can be achieved.

  However, if the substrate is destroyed on the stage during the stress application process, a maintenance operation is required with the processing chamber opened, and productivity is reduced. Therefore, it is desirable that the stress applied to the substrate in the stress application process is weaker than the predetermined stress, and the possibility that the substrate is destroyed during the stress application process is as low as possible.

  In this case, the stress applying step is performed by deforming the substrate having a shape that does not conform to the surface shape of the stage so as to follow the surface shape of the stage by the adsorption force of the adsorption means in the step of adsorbing the substrate to the stage. do it. In addition, in the initial stage of the heating process, it is also possible to perform the stress application process by heating the substrate in a state in which the substrate heating rate is slower than the subsequent heating rate, or by locally heating the substrate. . Further, when the heating process is performed by adsorbing the substrate to a preheated stage, the substrate is heated in a state where the adsorption force by the adsorption means is weaker than the subsequent adsorption force in the initial stage of the heating process. It is also possible to perform a stress application process. According to this, an increase in cycle time due to the addition of the stress application process can be suppressed by executing the stress application process during the adsorption process or the heating process.

Explanatory drawing which shows the installation used for implementation of this invention. Explanatory drawing which shows a deformation | transformation of a board | substrate when adsorb | sucking a board | substrate to a stage. Explanatory drawing which shows an example of the equipment for a preliminary inspection arrange | positioned in a place different from a process chamber. Explanatory drawing which shows the modification of the equipment for preliminary inspection arrange | positioned in a place different from a process chamber. Explanatory drawing which shows the other modification of the equipment for preliminary inspection arrange | positioned in a place different from a process chamber.

  Referring to FIG. 1, reference numeral 1 denotes a processing chamber in which a substrate S made of a silicon wafer is subjected to processing such as baking including a step of heating the substrate S to a predetermined processing temperature (for example, 400 ° C.). The bottom of the processing chamber 1 is closed with a cover plate 2, and the processing chamber 1 is brought into a vacuum state by a vacuum pump (not shown). A stage 3 on which the substrate S is placed is provided on the lid plate 2. The stage 3 incorporates suction means (not shown) made of an electrostatic chuck that sucks the substrate S and heating means (not shown) that heats the substrate S. The heating means includes a heater, a means for flowing a heating gas between the substrate S and a fine recess formed on the surface of the stage 3. It is also possible to configure the heating means with a heating lamp or the like disposed in the space above the stage 3 without incorporating the heating means into the stage 3. Further, if the processing chamber 1 is not in a vacuum state, a vacuum chuck may be used as the suction means.

  When processing the substrate S, first, the substrate S is loaded into the processing chamber 1 by a transfer robot (not shown) and placed on the stage 3. Next, a heating step is performed in which the substrate S is adsorbed on the surface of the stage 3 by the adsorbing means, and the substrate S is heated to the processing temperature by the heating means in this state.

  When the substrate S is heated in this way, the substrate S is thermally expanded in a state where it is restrained by adsorption to the stage 3, and stress is applied to the substrate S. When the substrate S is rapidly heated to the processing temperature, the stress applied to the substrate S becomes strong and the substrate S may be destroyed.

  Here, when stress is applied to the substrate S, an elastic wave is generated in the substrate S due to an acoustic emission (AE) phenomenon. This elastic wave propagates to the cover plate 2 via the stage 3. Therefore, the AE sensor 4 for detecting elastic waves is fixed to the lower surface of the cover plate 2 with an epoxy adhesive or the like. The AE sensor 4 may be fixed to the stage 3.

  When the substrate S is destroyed, the waveform of the frequency spectrum obtained by Fourier transforming the detection signal of the AE sensor 4 is a unique waveform having peaks at a plurality of frequencies in a high frequency region of 100 kHz to 1 MHz. When it is determined from the waveform analysis of the frequency spectrum that an elastic wave due to the destruction of the substrate S has occurred, further processing is stopped.

  However, once the substrate S is destroyed on the stage 3, laborious maintenance work such as opening the processing chamber 1 and removing fragments of the substrate S is required, and the productivity is greatly reduced.

  Therefore, in the present embodiment, the substrate S is placed on the stage 3 and the stress application step of applying stress to the substrate S and the AE phenomenon caused by the stress applied in the stress application step before the heating step is completed. Whether or not the substrate S can withstand strong stress applied in the heating process based on the elastic wave detected in the detection process. Judging. Hereinafter, the preliminary inspection will be specifically described.

  The substrate S may be warped as shown in FIG. 2A due to the influence of pretreatment such as film formation. In this case, in the step of adsorbing the substrate S to the stage 3, the substrate S having a shape that does not follow the surface shape of the stage 3 is aligned with the surface shape of the stage 3 as shown in FIG. Deform. In addition, irregularities may remain on the surface of the stage 3 due to the processing accuracy of the stage 3, and in this case, the substrate S is deformed so as to follow the surface shape of the stage 3 in the adsorption process. Therefore, the first stress applying step is executed by applying stress to the substrate S due to the deformation of the substrate S in the adsorption step.

  In addition, after completion of the adsorption process, in the initial stage of the heating process (specifically, until the temperature of the substrate S rises to a predetermined inspection temperature (for example, normal temperature + 100 ° C.) lower than the processing temperature). The second stress application step is performed by heating the substrate S in a state where the temperature increase rate is slower than the subsequent temperature increase rate. For example, when heating the substrate S by flowing a heating gas over the surface of the stage 3, the heating gas supply pressure is lowered to the middle of the heating step to slow the temperature rise rate of the substrate S, and then the heating gas supply pressure is increased. To increase the heating rate of the substrate S.

  Note that the stress applied to the substrate S in the first stress applying step is weaker than the stress applied to the substrate S in the heating step performed after the substrate adsorption. Further, the stress applied to the substrate S in the second stress applying step is also weaker than the stress applied to the substrate S in the latter half of the heating step in which the temperature rising rate is increased because the temperature rising rate of the substrate S is slowed down. . Therefore, the possibility that the substrate S is destroyed in the first and second stress application steps is extremely low. Furthermore, since the first and second stress application steps are performed during the adsorption step and the heating step, an increase in cycle time due to the addition of the stress application step can be suppressed.

  The substrate S is locally heated in the initial stage of the heating process, and a second stress is applied by applying stress to the substrate S due to a difference in thermal expansion between the heated portion and the non-heated portion of the substrate S during the local heating. It is also possible to carry out the process.

  Here, if a micro crack is generated in the substrate S in each stress application process, the micro crack may grow and cause the destruction of the substrate S when a strong stress is applied to the substrate S in the subsequent heating process. high. When a microcrack occurs, the waveform of the frequency spectrum obtained by Fourier transforming the detection signal of the AE sensor 4 peaks at a plurality of frequencies in a high frequency region of 100 kHz to 1 MHz, although the peak intensity is different from that when the substrate S is broken. It has a unique waveform.

  Therefore, the elastic wave generated on the substrate S in each of the first and second stress applying steps is detected by the AE sensor 4, and the waveform analysis in the high frequency region of 100 kHz to 1 MHz of the frequency spectrum of the detected elastic wave is performed, and the detected elastic wave is detected. It is determined whether or not an elastic wave generated by a microcrack is included. Specifically, the degree of coincidence is calculated for various parameters (peak frequency, peak intensity, rise time, decay time, etc.) of the frequency spectrum waveform compared to that at the time of occurrence of a microcrack, and the degree of coincidence is not less than a predetermined threshold. If so, it is determined that a microcrack has occurred. In this case, it is determined that the substrate S cannot withstand the stress applied in the heating process, the heating process is stopped, and the substrate S is removed from the processing chamber 1 by the transfer robot. Thereby, possibility that the board | substrate S will destroy on the stage 3 can be reduced as much as possible.

  By the way, when a micro crack is generated in the first stress application step, the adsorption of the substrate S by the adsorption unit is released prior to carrying out the substrate S. At this time, the substrate S is deformed so as to follow the surface shape of the stage 3. There is a possibility that the substrate S that has been bounced back and micro cracks grow due to the impact of the bounce and the substrate S is destroyed. Here, the impact caused by the rebound of the substrate S increases as the suction force increases. Therefore, in order to suppress the breakage due to the rebound of the substrate S when the suction is released, in the first stress application step, when the suction force of the substrate S is weakened and no microcracks are generated, the suction force is set to a normal value. It is desirable to increase to the value.

  Also, the heating process may be performed by adsorbing the substrate S to the stage 3 heated to a high temperature in advance. In this case, in the initial stage of the heating process, it is possible to execute the second stress applying process by heating the substrate S in a state where the suction force by the suction means is weaker than the subsequent suction force. That is, if the attracting force is weakened, the restraining force for pressing the substrate S against its thermal expansion decreases, so that a stress that is weaker than the stress applied to the substrate S in the latter half of the heating process is applied to the substrate S. An application process can be performed.

  It should be noted that a stage for attracting and heating the substrate S may be arranged at a place for preliminary inspection different from the processing chamber 1 to execute the first stress applying step and the second stress applying step. .

  Moreover, it is also possible to arrange the equipment shown in FIG. 3 in a place for preliminary inspection and perform preliminary inspection. This equipment includes a support member 11 having a plurality of pin portions 11a for supporting the substrate S, an AE sensor 12 supported by the support member 11 via a spring 12a so as to contact the substrate S, and the substrate S. And an oscillator 13 that emits ultrasonic waves (for example, 39 kHz). In addition, you may attach the AE sensor 12 to the upper end part of either pin part 11a.

  When ultrasonic waves are radiated from the oscillator 13 in the atmosphere, the substrate S receives the ultrasonic waves and vibrates, stress is applied to the substrate S, and elastic waves generated on the substrate S due to the AE phenomenon caused by the stress are generated by the AE sensor. 12 is detected. Then, a waveform analysis in a high frequency region of 100 kHz to 1 MHz of the frequency spectrum of the detected elastic wave is performed, and when it is determined that the detected elastic wave includes an elastic wave generated by a microcrack, the substrate S is added in the subsequent processing. It is determined that it cannot withstand the stress, and the subsequent processing for the substrate S is stopped.

  Moreover, the equipment arranged at the place for the preliminary inspection may be as shown in FIG. This equipment includes a support member 21 having an annular protrusion 21a on the upper surface that supports the substrate S, an oscillator 23 that is attached to a frame 22 facing the substrate S and radiates ultrasonic waves toward the substrate S, and a substrate S. And a receiver 24 for receiving ultrasonic waves emitted from the receiver.

  When ultrasonic waves are radiated from the oscillator 23 in the atmosphere, the substrate S receives the ultrasonic waves and vibrates, stress is applied to the substrate S, and elastic waves generated in the substrate S due to the AE phenomenon due to the stress are generated in the air. Is propagated as an ultrasonic wave and detected by the receiver 24. However, the receiver 24 also detects the ultrasonic wave reflected by the substrate S. Therefore, the ultrasonic radiation from the oscillator 23 is turned on / off in a short cycle (for example, 10 ms), and the ultrasonic wave radiated from the substrate S is detected by the receiver 24 immediately after the ultrasonic radiation is turned off. Then, a waveform analysis of the frequency spectrum of the detected ultrasonic wave is performed, and when it is determined that the detected ultrasonic wave includes an ultrasonic wave caused by an elastic wave generated by a microcrack, the substrate S is added in the subsequent processing. It is determined that the substrate cannot be tolerated, and the subsequent processing for the substrate S is stopped.

  Note that at least the pin portion 11a of the support member 11 shown in FIG. 3 and the annular protrusion 21a of the support member 21 shown in FIG. 4 are desirably formed of resin or rubber that is difficult to transmit high-frequency vibrations. According to this, disturbance vibration from the support members 11 and 21 can be removed, and the inspection accuracy is improved.

  In addition, as shown in FIG. 5, it is possible to perform a preliminary inspection in a state where a plurality of substrates S are accommodated in a container C. In this case, the probe 31 having the ultrasonic wave transmitting section and the receiving section is moved to the same level as each substrate S in the container C by an elevator mechanism (not shown) in a state where the probe 31 is brought close to the container C. Then, at each position, the ultrasonic radiation from the probe 31 is turned on and off in a short cycle, and the ultrasonic wave emitted from the substrate S is detected by the probe 31 immediately after the ultrasonic radiation is turned off. Next, a waveform analysis of the frequency spectrum of the detected ultrasonic wave is performed in the same manner as described above, and when it is determined that the detected ultrasonic wave includes an ultrasonic wave caused by an elastic wave generated by a microcrack, the substrate S Since it is determined that it cannot withstand the stress applied by the processing, the subsequent processing on the substrate S is stopped.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to this. For example, in the above-described embodiment, the present invention is applied to a preliminary inspection of a substrate made of a silicon wafer, but the present invention can be similarly applied to a preliminary inspection of a substrate other than a silicon wafer such as a glass substrate or a gallium substrate. .

  In the embodiment shown in FIGS. 3 to 5, ultrasonic waves are radiated to apply stress to the substrate S. However, sound waves may be radiated, and furthermore, a differential pressure is generated above and below the substrate. It is also possible to apply a stress to the substrate by causing the substrate to warp, or warping, pulling, compressing, or shaking the substrate across the edge of the substrate.

  Moreover, in the said embodiment, although the process in which predetermined | prescribed stress is added to the board | substrate S is a heating process, the process including the cooling process which cools a high temperature board | substrate, and the process of applying physical stress other than heat to a board | substrate are included. The present invention can be similarly applied to a preliminary inspection performed before processing.

S ... substrate, 1 ... processing chamber, 3 ... stage, 4, 12 ... AE sensor.

Claims (6)

Before performing a process that includes a step of applying a predetermined stress to the substrate, a stress applying step of applying stress to the substrate and an acoustic wave generated on the substrate by an acoustic emission phenomenon caused by the stress applied in the stress applying step. A substrate pre-inspection method for determining whether the substrate can withstand the predetermined stress based on the elastic wave detected in the detection step .
The process is a process performed in a processing chamber including a stage having an adsorption unit that adsorbs a substrate and a heating unit that heats the substrate, and the step of applying the predetermined stress is performed while the substrate is adsorbed on the stage. The stress applying step and the detecting step are performed before the heating step is completed in a state where the substrate is placed on the stage, and the stress applying step heats the substrate. And a substrate pre-inspection method, wherein the stress applied to the substrate is weaker than the predetermined stress . 2. The elastic wave detected in the detection step includes an elastic wave generated by a micro crack generated before the substrate is broken, and it is determined that the substrate cannot withstand the predetermined stress. The substrate pre-inspection method described . Before SL stress application step is the in the step of adsorbing the substrate to the stage is carried out by deforming along the substrate shape does not follow the surface shape of a stage on the surface shape of the stage in the suction force of the suction means The substrate preliminary inspection method according to claim 1 . The stress application step in the initial stage of the heating step, the substrate advance according to claim 1, characterized in that is carried out by heating the substrate heating rate of the substrate in a subsequent state of being slower than the heating rate of the Inspection method. The stress application step in the initial stage of the heating step, substrate pre-inspection method according to claim 1, wherein the is performed by locally heating the substrate. In those performing the heating step by adsorbing the substrate to a pre-Me heated stage, the stress application step in the initial stage of the heating step, the suction force by the suction means in the subsequent state of being weaker than the suction force The substrate preliminary inspection method according to claim 1, wherein the substrate preliminary inspection method is performed by heating the substrate.

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